Can cytology accurately predict benign follicular nodules?

The reliability of fine-needle aspiration (FNA) biopsy in differentiating benign from malignant follicular lesions of the thyroid has been the subject of renewed debate recently. Although surgical excision has been recommended for most follicular lesions identified by cytology, this approach may not be necessary in all cases. The goal of this study was to determine whether FNA could be used as a diagnostic tool to safely identify patients with follicular thyroid nodules who do not require immediate surgical intervention.

A retrospective review was performed on a sample of 24 patients diagnosed with either follicular adenoma or follicular carcinoma after surgical excision of a thyroid nodule. The initial FNA biopsies were independently reviewed by two experienced cytopathologists in a blinded fashion and subsequently compared with final histologic diagnoses.

For pathologist A, overall accuracy was 58%. The positive predictive value (PPV) of a benign diagnosis was 82%; PPV of a malignant diagnosis was 38%. For pathologist B, overall accuracy was 63%. The PPV of a benign diagnosis was 83%; PPV of a malignant diagnosis was 42%.

This study suggests that in follicular lesions of the thyroid, a benign FNA biopsy report from an experienced cytopathologist has a high positive predictive value. The predictive value may not, however, be high enough to preclude surgery; other factors may need to be considered before recommending a nonoperative approach.